The invention relates to electrical couplers, and more particularly relates to electrical couplers that are used in environmentally exposed applications. In its most immediate sense, the invention relates to electrical couplers such as those used between railroad cars.
Typically, electrical connections between adjacent railroad cars are made using pairs of couplers. Each coupler is connected to an end of a car. When two cars are connected to each other (as by adding a car to the end of an existing train) the couplers at the adjacent ends of the cars are also connected to each other. Each coupler has a plurality of spring-loaded electrically conductive pins, and when adjacent cars are connected together corresponding pins on the couplers press against each other to establish the necessary electrical connections between the cars. In use, corresponding pins on the couplers can move in and out, but are urged outwardly from the couplers so as to be butted tightly against each other because of the forces exerted by the springs. With such a structure, the electrical connection between each two corresponding pins may be maintained even when the train travels around a curve; the pins on the inside of the curve are pressed inwardly against the springs to accommodate the reduced distance between the cars, and the pins on the outside of the curve are urged outwardly by the springs to make up for the increased distance between the cars. It may therefore be understood that motion of the pins is necessary to maintain the desired electrical connections between adjacent cars; if the motion does not occur, the desired electrical connections will not be maintained when the cars move with respect to each other (as when rounding a curve). In such instances, corresponding pins will become separated from each other, causing open circuits and arcing.
Conventional couplers fail because the pins become stuck in position. This in turn comes about because the couplers are exposed to the weather, and over time moisture gets into the pin mechanisms. The moisture causes corrosion, which in turn causes the pins to bind. Furthermore, even if corrosion has not yet occurred, cold weather causes the moisture to freeze and therefore likewise causes the pins to bind. While bound-in-position pins will sometimes break free as the couplers move towards and away from each other during use, the pin mechanisms eventually fail so that pin motion cannot be restored. When this happens, the coupler must be serviced.
It would be advantageous to provide an electrical coupler that would be less subject to failure caused by corrosion from moisture or by freezing during cold weather.
In accordance with the invention, a heated coupler is provided. The coupler has a plurality of electrical connectors. Each connector has a generally cylindrical body, a spring-loaded, electrically conductive pin retained within the body in such a manner as to project axially outwardly from the body and as to be capable of moving axially inwardly into the body against spring pressure when so urged by a mating pin on a mating coupler, and a terminal for making an electrical connection with the pin. The coupler also has a coupler body. The coupler body has a front surface, a rear surface and a like plurality of recesses extending between the front and rear surfaces. Each recess is dimensioned to receive a corresponding one of the connectors in such a manner that the pins project forwardly out of the front surface of the coupler body and the terminals project rearwardly out of the rear surface of the coupler body. The coupler also has an electrical resistance element located in the coupler body adjacent the rear surface, and a backing plate having a like plurality of holes, the backing plate being secured to the coupler body and retaining the connectors therein in such a manner that the terminals project through the holes for connection to a wiring harness.
Advantageously, and in accordance with the preferred embodiment, the connectors and recesses are arranged in elongated rows. The coupler body has channels in the rear surface and the channels extend between each two adjacent rows. The electrical resistance element is located in the channels and the channels are sealed with an epoxy adhesive. Advantageously, a thermostat is used to keep the temperature of the coupler body within a predetermined range.
Experiments with prototypes of the invention have shown that the electrical resistance element delivers sufficient heat to prevent freezing and to evaporate moisture on the pins in cold weather as well as warm weather. This dries out the pin mechanisms of the coupler before moisture can cause corrosion and before moisture can turn to ice, thereby prolonging the service life of the pin mechanisms and reducing the frequency with which the coupler must be serviced. Additionally, the electrical resistance element is not subject to any substantial mechanical forces and therefore can be expected to require little servicing on its own. Furthermore, these results are achieved without so raising the temperature of the coupler as to present a possible hazard to maintenance personnel.